GEE Workspace tutorial - Create a slope map for the alpine arc

Tutorial walkthrough

Note

This is a good idea to think to save the state of your workspace time to time.

Load the SRTM 30m digital elevation product

Click on add data

Search for SRTM elevation, click on the SRTM 30m digital elevation Data product

Click on the question mark icon to get further information on the selected product.

Produce the slope and aspect maps

Click on add computation

Select Slope and aspect. Then select the elevation maps as reference. By default the visualization will be based on a combination both elevation and aspect (RGB).

Display the slope map in a nice way

To make it simpler we will here just focus only on the slope band.
Click on the Slope and aspect product on the left panel, select the Slope band, and setup the color scale to cover 100% of the slope range (0-90).

Here we are on a grey-scale. We can choose to define our own color-scale. You can for instance use the excellent website http://colorbrewer2.org/ to generate a html color-scale that suits you.

I choose here this color-scale:

ffffcc,ffeda0,fed976,feb24c,fd8d3c,fc4e2a,e31a1c,bd0026,800026

You can easily set it clicking on Palete then on the pen icon and pasting your colors scale in hexadecimal format.

You should now have something like:

Export an image of the slope map of alpine arc (as .jpg)

Click on the slope map feature in the left panel, then click on the downloading arrow. Select the area, projection system and resolution that suits you and click on Download.

A window will pop-up..

Click ok … You are done !!!

Note: In case you didn’t manage to make it or if you want to compare you results to mine you can use one of the following sections.

Link to the final workspace

Here is the link to the final workspace

JSON version of the final workspace

Here is the Json version of the final workspace. You can copy this lines and import them in your workspace.

{
  "viewport": {
    "zoom": 10,
    "lat": 45.22267719962014,
    "lng": 5.9161376953125
  },
  "name": "",
  "classmodel": [],
  "polylayers": [],
  "datalayers": [
    {
      "title": "Computed layer: Slope And Aspect",
      "originaltitle": null,
      "overlayvisible": true,
      "vis": {
        "opacity": 0.51,
        "bands": [
          "slope"
        ],
        "max": 44,
        "palette": [
          "ffffcc",
          "ffeda0",
          "fed976",
          "feb24c",
          "fd8d3c",
          "fc4e2a",
          "e31a1c",
          "bd0026",
          "800026"
        ],
        "format": "png"
      },
      "layermode": "advisory-mode",
      "datatype": "computed",
      "computations": [
        {
          "title": "1. Slope And Aspect",
          "operation": "TerrainSlopeAspect",
          "layer": {
            "image": {
              "type": "Invocation",
              "arguments": {
                "id": "USGS/SRTMGL1_003"
              },
              "functionName": "Image.load"
            },
            "bands": [
              "elevation"
            ],
            "title": "SRTM Digital Elevation Data 30m"
          }
        }
      ]
    },
    {
      "title": "SRTM Digital Elevation Data 30m",
      "originaltitle": null,
      "overlayvisible": false,
      "vis": {
        "opacity": 1,
        "bands": [
          "elevation"
        ],
        "min": 0,
        "max": 6000,
        "gamma": 1.6
      },
      "layermode": "advisory-mode",
      "datatype": "image",
      "assetid": "USGS/SRTMGL1_003"
    }
  ],
  "drawnpoints": [],
  "drawnpolys": [],
  "analysis": null
}